Field of the Invention
The present invention relates to a solid state imaging device, a manufacturing method of a solid state imaging device, and an imaging system.
Description of the Related Art
In solid state imaging devices such as a CMOS image sensor, a CCD image sensor, and the like are provided with a light shielding member that prevents a light from entering portions other than a photoelectric conversion unit that performs a photoelectric conversion. For example, a CMOS image sensor having a global electronic shutter (all-pixel corrective simultaneous exposure) function has a charge holding unit that holds charges transferred from a photoelectric conversion unit. With a light entering the charge holding unit and causing a photoelectric conversion, the photoelectric-converted charges may be likely to cause noise resulting in degradation of an image quality. Therefore, the charge holding unit is covered with a light shielding member to prevent an incidence of a light. Further, in a CCD image sensor, similarly to the CMOS image sensor, a reading out unit is covered with a light shielding member, because an incidence of a light to the reading out unit may cause noise.
In a solid state imaging device having a light shielding member, since there is an optically transparent interlayer insulating film between a substrate and a light shielding member, it is intended to improve the light shielding property by preventing an incoming light through the interlayer insulating film. Japanese Patent Application Publication No. 2012-248681 discloses that the film thickness of an insulating layer is reduced by etching the insulating layer disposed under a light shielding member. A leakage of a light to a charge holding unit is suppressed by reducing the thickness of the insulating film under the light shielding member to reduce the distance between a photoelectric conversion unit and an under surface of a light shielding member in order to improve of the light shielding property.
When an insulating film is formed on neighboring gate electrodes and a light shielding film is deposited thereon, a certain size of a gap between gate electrodes is less likely cause a residue even when the light shielding film is etched, because there is a portion where the insulating film is sufficiently flat between the gate electrodes.
On the other hand, refinement in a semiconductor process results in a narrower gap between gate electrodes. After a light shielding film that becomes a light shielding member is deposited on this narrow gap and the light shielding member is etched, a residue of the light shielding film may remain inside the narrow gap. Such a residue may cause a leakage. In Japanese Patent Application Publication No. 2012-248681, an insulating film is deposited under a light shielding film to fill a recess between gate electrodes and between wirings and reduce a level difference. This can reduce occurrence of an etching residue of the light shielding film. In Japanese Patent Application Publication No. 2012-248681, however, while a recess narrower than a certain spacing can be filled, a recess wider than or equal to the certain spacing cannot be fully filled and a thin gap remains, and the light shielding member may remain in the gap. Even when the thickness of the insulating film to be filled is increased, a gap may occur depending on a spacing and thus occurrence of a residue cannot be completely prevented.
Further, when the flatness of an insulating film surface is degenerated due to a level difference around gate electrodes, the flatness of a light shielding member and a structure formed thereon is also degenerated, which may reduce a yield rate. One of the objects of the present invention is to provide a solid state imaging device, a manufacturing method of a solid state imaging device, and an imaging system that can maintain a light shielding property of a light shielding member and improve a yield rate.